1.Login to Plesk.
2.Click on 'Domains' under Main Menu.
3.Select the domain you want to set 'Scheduled Backup Setting'.
4.Click on 'Backup Manager'.
5.Select 'Scheduled Backup Settings' under Tools Menu.
6.Enable the option 'Activate this backup task'.
7.Limit the number of backups in server repository by setting required value in 'Maximum number of backups in repository'.
8.Enter the required details.